ROUND HILL - Lake Tahoe has seen a dramatic reduction in levels of burned and unburned gasoline products in its water since two-stroke, carburetor engines were banned in 1999, water quality officials said.
"As much as it was difficult to replace fleets of Jet Skis, it was well worth it," said Rita Whitney, a hydrologist for the Tahoe Regional Planning Agency.
"I want people to know their hardship paid off in terms of conclusive data that shows a definite reduction in loading of gasoline products to the lake."
Whitney said levels of gasoline products in the lake has declined 80 percent to 90 percent.
The ban was instituted by the TRPA's, bi-state governing board after a study estimated that each day of the boating season, two-stroke engines released 770 gallons of unburned fuel into the lake.
The large decrease in the amount of gasoline products in Lake Tahoe is safer for residents who rely on the lake as a source for drinking water and healthier for fish and wildlife, Whitney said.
Most of the people who drink lake water live on the Nevada side of the basin. At one point prior to the ban, residents on Elks Point, near Round Hill, tasted a turpentine-like flavor in their water. It turned out the gasoline additive MTBE had tainted their drinking water supply.
"The state health department had Elks Point shut down the intake and drill a well," Whitney said.
Before the ban, businesses that rent boats and personal watercraft feared having to convert their fleets to more expensive four-stroke machines would force them out of business.
But TRPA spokeswoman Julie Regan said that fear was unfounded, because no businesses ended up closing.
Ron Williams, owner of Ski Run Boat Co., said the ban forced him to spend $302,000 to purchase 36 four-stroke Yamaha WaveRunners.
"We of course abided by the law and changed all our motors from two-stroke to four- stroke," Williams said. "But we weren't able to raise (rental) prices to reflect the increase in cost. I don't think the consumers would have stomached that."
Williams said while he's happy the lake is healthier, he hasn't noticed any change in water quality.
"I thought any gasoline vapors emitted into the lake dissipated in 72 hours, so I don't know," Williams said. "All I know is I'm glad to be living in a beautiful place and have a beautiful place to recreate in."
Research done at the request of the TRPA determined that fuel, burned and unburned, being released into the lake does have long-term impacts.
"Particles from the burned fuel were attaching to fine sediment and other particles in the lake and going to the bottom," Regan said. "Part of the problem was also MTBE. We know from its impacts on the water supply at South Shore that it doesn't evaporate or dissipate."
Even with the ban, gasoline products still end up in the lake. A carbureted two-stroke dumps about 30 percent of its fuel into the water.
Four-stroke and fuel-injected two strokes, which are the type of engines allowed on the lake, release between 1 and 2 percent, Whitney said.
The TRPA outfits its watercraft enforcement boat with a direct injection two-stroke engine to show boaters that the ban does not include all two-stroke engines, only carbureted ones.
The agency has a deal with Evinrude, a boat engine manufacturer, that allows the TRPA to use its latest fuel-injected, two-stroke engine.
The agency is scheduled to receive Evinrude's 2005 E-TEC engine, its most environmentally friendly and powerful model to date, this fall.
According to Evinrude, the engine releases no unburned oil-gas into the water and burns all the oil put in the engine, which eliminates the need to recycle oil.
"It's a whole new technology based on the two-stroke," said David Thompson, director of communications for Bombardier Recreational Products, which manufactures Evinrude engines. "E-TEC is our response to the market. As society moved forward, people wanted cleaner engines, quieter engines and more fuel-efficient engines."
